1. C program to swap two numbers using four different methods.

#include 

int main()
{
  int a, b, t;
  printf(" Enter value of A ?  ");
  scanf("%d", &a);
  printf(" Enter value of B ?  ");
  scanf("%d", &b);

  printf("\n Before swapping : A= %d, B= %d", a, b);

  /****first method using third variable*/
  t = a;
  a = b;
  b = t;
  printf("\n After swapping (First method) : A= %d, B= %d\n", a, b);

  /****second method without using third variable*/
  a = a + b;
  b = a - b;
  a = a - b;
  printf("\n After swapping (second method): A= %d, B= %d\n", a, b);

  /****Third method  using X-Or */
  a ^= b;
  b ^= a;
  a ^= b;
  printf("\n After swapping (third method) : A= %d, B= %d\n", a, b);

  /****fourth method  (single statement)*/
  a = a + b - (b = a);
  printf("\n After swapping (fourth method): A= %d, B= %d\n", a, b);

  return 0;
}

#include 
#include 
using namespace std;

void swap(int arr[], int pos1, int pos2)
{
  int temp;
  temp = arr[pos1];
  arr[pos1] = arr[pos2];
  arr[pos2] = temp;
}

int partition(int arr[], int low, int high, int pivot)
{
  int i = low;
  int j = low;
  while (i <= high)
  {
    if (arr[i] > pivot)
    {  i++;
    }
    else
    {  swap(arr, i, j);  i++;  j++;
    }
  }
  return j - 1;
}

void quickSort(int arr[], int low, int high)
{
  if (low < high)
  {
    int pivot = arr[high];
    int pos = partition(arr, low, high, pivot);  quickSort(arr, low, pos - 1);
    quickSort(arr, pos + 1, high);
  }
}

int main()
{
  int arr[] = {2, 5, 3, 7, 1, 9};
  quickSort(arr, 0, 6 - 1);
  cout << "The sorted array is: ";
  for (int i = 0; i < 6; i++)
  {
    cout << arr[i] << " ";
  }
}